You need to post the error message lest others don't be bothered to look it up (there are thousands of them -too many to remember). I didn't look up that number but I suspect your subform reference is wrong:
[Forms]![Main form name]![subform control name].[Form]![control name on subform]
subform control name is the name of the subform control, which may not be the same as the subform itself.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.